package com.xiaoh.nio;

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Arrays;

/**
 * Scattering：将数据写入到buffer时，可以采用buffer数组，依次写入
 * Gathering：从buffer读取数据时，可以采用buffer数组，依次读写
 *
 * @author xiaoH
 * @date 2020/5/4
 * @description
 */
public class ScatteringAndGatheringTest {

    public static void main(String[] args) throws Exception {
        // 使用ServerSocketChannel 和 SocketChannel
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        InetSocketAddress inetSocketAddress = new InetSocketAddress(7000);

        //绑定端口到socket，并启动
        serverSocketChannel.socket().bind(inetSocketAddress);

        //创建buffer数组
        ByteBuffer[] byteBuffers = new ByteBuffer[2];
        byteBuffers[0] = ByteBuffer.allocate(5);
        byteBuffers[1] = ByteBuffer.allocate(3);

        //等客户端连接（telnet）
        SocketChannel socketChannel = serverSocketChannel.accept();
        int messageLength = 8;//假设从客户端接收8个字节

        //循环的读取
        while (true) {
            int byteRead = 0;
            while (byteRead < messageLength) {
                long l = socketChannel.read(byteBuffers);
                byteRead += l;//累计读取的字节数
                System.out.println("byteRead=" + byteRead);

                //使用流打印，看看当前的这个buffer的position和limit
                Arrays.asList(byteBuffers).stream().map(buffer -> "position=" + buffer.position() + ", limit=" +
                        buffer.limit()).forEach(System.out::println);
            }

            //将所有的buffer进行反转flip
            Arrays.asList(byteBuffers).forEach(buffer -> buffer.flip());

            //将数据读出显示到客户端
            long byteWrite = 0;
            while (byteWrite < messageLength) {
                long l = socketChannel.write(byteBuffers);
                byteWrite += l;
            }

            //将所有的buffer进行clean
            Arrays.asList(byteBuffers).forEach(buffer -> buffer.clear());

            System.out.println("byteRead= " + byteRead + ", byteWrite=" + byteWrite + ", messageLength=" + messageLength);
        }
    }
}
